zlib/minizip: Update to version 1.2.12

Security update, fixes CVE-2018-25032 in zlib.

Preliminary assessment doesn't show Godot as affected since we don't
seem to call `deflate` with the problematic parameters, but the extent
of the vulnerability is not fully clear upstream yet.

(cherry picked from commit 420d0d50bc)

thirdparty/minizip/crypt.h

@@ -38,6 +38,7 @@ static int decrypt_byte(unsigned long* pkeys, const z_crc_t* pcrc_32_tab)
                      * unpredictable manner on 16-bit systems; not a problem
                      * with any known compiler so far, though */
 
+    (void)pcrc_32_tab;
     temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2;
     return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
 }
@@ -77,24 +78,24 @@ static void init_keys(const char* passwd,unsigned long* pkeys,const z_crc_t* pcr
     (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab)))
 
 #define zencode(pkeys,pcrc_32_tab,c,t) \
-    (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c))
+    (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), (Byte)t^(c))
 
 #ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
 
 #define RAND_HEAD_LEN  12
    /* "last resort" source for second part of crypt seed pattern */
 #  ifndef ZCR_SEED2
-#    define ZCR_SEED2 3141592654UL     /* use PI as default pattern */
+#    define ZCR_SEED2 3141592654L       /* use PI as default pattern */
 #  endif
 
-static int crypthead(const char* passwd,      /* password string */
-                     unsigned char* buf,      /* where to write header */
-                     int bufSize,
-                     unsigned long* pkeys,
-                     const z_crc_t* pcrc_32_tab,
-                     unsigned long crcForCrypting)
+static unsigned crypthead(const char* passwd,       /* password string */
+                          unsigned char* buf,       /* where to write header */
+                          int bufSize,
+                          unsigned long* pkeys,
+                          const z_crc_t* pcrc_32_tab,
+                          unsigned long crcForCrypting)
 {
-    int n;                       /* index in random header */
+    unsigned n;                  /* index in random header */
     int t;                       /* temporary */
     int c;                       /* random byte */
     unsigned char header[RAND_HEAD_LEN-2]; /* random header */